Tripod type constant-velocity universal joint

ABSTRACT

A tripod type constant-velocity universal joint is provided in which a tripod member is prevented from coming out the outer ring. A guide block is supported on each trunnion of the tripod member mounted in the outer ring. Rolling elements are mounted between raceway grooves formed in both side faces of the guide blocks and raceway grooves formed in both sides of track grooves of the outer ring so that they will make a pure rolling movement over the entire moving range of the guide block. A lever is mounted to a plate portion of each retainer for retaining the rolling elements. Pins are inserted in a pair of guide grooves formed in the lever. One of the pins is secured to the outer ring and the other pin is secured to the guide block. A stopper ring is mounted to the open end of the outer ring, so that the stopper ring will prevent the rolling elements from coming out of the raceway grooves, thereby preventing the tripod member from coming out of the outer ring.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a tripod type constant- velocity universal joint in which torque is transmitted between an outer ring having three track grooves formed in the inner periphery thereof and a tripod member mounted therein so as to be axially movable.

[0002] A tripod type constant-velocity universal joint is known which comprises an outer ring formed with three axially extending track grooves in its inner periphery, a tripod member mounted in the outer ring and having three trunnions formed thereon, cylindrical roller guide surfaces formed in side faces of each track groove so as to oppose each other in the circumferential direction of the outer ring, the raceway grooves extending in the axial direction of the outer ring, a spherical roller supported on each trunnion so as to be pivotable relative to the trunnion and received in the each track groove for transmitting a torque between the outer ring and the tripod member.

[0003] With this tripod type constant-velocity universal joint, when torque is transmitted with the tripod member taking a working angle relative to the outer ring, the center of rotation of the spherical roller is inclined relative to the lengthwise direction of the track groove. Thus, the spherical roller cannot make a pure rolling movement, so that slip occurs between the spherical roller and the roller guide surface in the track groove.

[0004] This increases the frictional resistance at the contact point between the spherical roller and the roller guide surface and increases the slide resistance when the outer ring and the tripod member move axially relative to each other. Therefore, vibration and noise are produced and the NVH properties worsen.

[0005] A tripod type constant-velocity universal joint of this type is proposed in JP patent publication 64-5164 to improve the NVH properties. In this type universal joint, three track grooves are formed in the inner periphery of the outer ring and raceway grooves extending in the axial direction of the outer ring are formed in both sides of each track groove that oppose in a circumferential direction of the outer ring. Three trunnions are formed on the tripod member which is mounted in the outer ring. A guide block supported on each trunnion so as to be pivotable relative to the trunnion is received in the track groove. Balls are mounted between raceway grooves formed on both sides of each guide block and the raceway grooves formed in the outer ring to transmit torque between the outer ring and the tripod member through the balls.

[0006] In this tripod type constant-velocity universal joint, since the balls are mounted between the raceway grooves of the outer ring and the raceway grooves of the guide blocks, when torque is transmitted with the outer ring and the tripod member forming a working angle, the guide blocks move in an axial direction of the outer ring with their attitude kept constant. Since the balls always roll in contact with the raceway grooves as the tripod member moves relative to the outer ring, vibration and noise are extremely low, so that the NVH properties are good.

[0007] In the tripod type constant-velocity universal joint shown in the abovesaid publication, portions for preventing the balls from falling off have to be provided at both ends of each raceway groove of the guide blocks. Thus, when the working angle between the outer ring and the tripod member is large, the balls cannot roll smoothly and slip occurs because they contact the fall-preventive portions, so that in the slip region, the NVH properties worsen.

[0008] In order to avoid this problem, in the constant-velocity universal joint described in JP patent publication 4-74565, a plurality of balls mounted between the raceway grooves of the guide blocks and the raceway grooves at both sides of the track grooves of the outer ring are retained by a retainer and the moving distance of movement of the retainer is restricted to half of the moving distance of the guide blocks by a moving distance restricting means so that the balls can always do a pure rolling motion.

[0009] With a conventional tripod type constant-velocity universal joint, it was sometimes impossible to cause a plurality of rolling elements to make a pure rolling movement over the entire moving range of the guide block when there is certain relationship between the required moving distance of the guide block, the number of the rolling members, the pitch between the rolling members, the length of the guide block and the length of the track groove of the outer ring.

[0010] The first object of the present invention is to provide a tripod type constant-velocity universal joint which has good NVH properties.

[0011] With this already proposed tripod type constant- velocity universal joint, since the tripod member is movable in the axial direction of the outer ring, during transportation or while mounting on an automobile, the tripod member may come off the outer ring. If the tripod member comes off, the rolling elements would fall off the retainer. Moreover, since the open end of the outer ring is closed by a boot, it is impossible to reassemble parts such as the tripod member.

[0012] The second object of this invention is to prevent the tripod member from falling in such a tripod type constant-velocity universal joint.

SUMMARY OF THE INVENTION

[0013] According to this invention, in order to solve the first object, there is provided a tripod type constant- velocity universal joint comprising an outer ring formed with three axially extending track grooves in inner periphery thereof, a tripod member mounted in the outer ring and having three trunnions formed thereon so as to oppose the track grooves, raceway grooves formed in side faces of the each track groove opposing each other in the circumferential direction of the outer ring, the raceway grooves extending in the axial direction of the outer ring, a guide block supported on the each trunnion so as to be pivotable relative to the trunnion and received in the each track groove, the guide block being formed with a raceway groove in side faces thereof, a plurality of rolling elements mounted between the raceway groove formed in side faces of the each guide block and the each raceway groove of the outer ring, retainers for retaining the rolling elements, and a moving distance restricting means for restricting the moving distance of the each retainer to half of the moving distance of the guide block, characterized in that the rolling members are adapted to roll over the entire moving range in the axial direction of the outer ring.

[0014] By adapting that a plurality of the rolling elements will roll over the entire moving range of the guide block, a tripod type constant-velocity universal joint is provided which has good NVH properties.

[0015] By setting the length of the raceway groove of the outer ring and the length of the guide block to meet the following formula:

K=(n−1)·A+L/2

B>A when n=2, B>2A when n>3

[0016] wherein

[0017] a: Diameter of the rolling elements

[0018] A: Pitch between the rolling elements

[0019] B: Length of the guide block

[0020] L: Required moving distance of the guide block

[0021] K: Length of the track groove of the outer ring

[0022] n: Number of rolling elements mounted in one raceway groove

[0023] a tripod type constant-velocity universal joint is provided which has good NVH properties and in which a plurality of rolling elements roll over the entire moving range of the guide block.

[0024] With the tripod type constant-velocity universal joint of this invention, the guide block generally requires a moving distance of 40 mm or over in view of the maximum operating angle and the radius from the center of the outer ring to the center of the rolling element. If the universal joint is designed with two rolling elements, the lengths of the guide block and the outer ring would be too long and the total weight would increase. If the number of the rolling elements is larger than necessary, it would increase the length of the rolling elements and the weight of the universal joint. Thus it is preferable that the number of the rolling elements is three.

[0025] According to this invention, in order to solve the second object, a stoper ring is mounted to the open end of the outer ring to prevent the rolling elements from coming out of the outer ring.

[0026] By mounting the stopper ring to the open end of the outer ring, it is possible to prevent not only the rolling elements but also the retainer from coming out. By preventing the retainer from coming out, the lever provided as the moving distance restricting means is prevented from turning in one direction, so that the pin on the guide block is kept engaged in the guide groove of the lever. Thus it is possible to prevent the guide blocks and the tripod member from coming out of the open end of the outer ring.

[0027] The stopper ring has an annular plate portion abutting the open end of the outer ring, and a cylindrical portion provided on the outer periphery of the annular plate portion and fitted on the outer periphery of the open end of the outer ring. The annular plate portion is formed with cutouts at positions opposing the open ends of the track grooves, and protrusions are provided on both sides of each cutout and inserted in the raceway grooves of the outer ring to prevent the rolling elements from coming out of the open ends of the track grooves.

[0028] In an arrangement in which a pin-forming piece is formed on the inner periphery of each cutout of the annular plate portion of the stopper ring so as to be inserted in each track groove, and the pin secured to the outer ring is formed by pressing on each pin-forming piece.

[0029] By forming the stopper ring by pressing a metallic plate, it is possible to easily form the stopper ring, so that it is possible to reduce the cost of the tripod type constant-velocity universal joint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:

[0031]FIG. 1 is a vertical sectional front view of the tripod type constant-velocity universal joint embodying this invention;

[0032]FIG. 2 is a partially cutaway side view of the same;

[0033]FIG. 3 is a sectional view taken along III-III of FIG. 2;

[0034] FIGS. 4A-4C are views showing positional relationship between the outer ring, retainer and guide block;

[0035]FIG. 5 is a partially cutaway side view of another embodiment of the universal joint;

[0036]FIG. 6 is a similar view of a further embodiment;

[0037]FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;

[0038] FIGS. 8A-8C are views for explaining how the length of the track groove of the outer ring is determined;

[0039]FIG. 9 is a partially cutaway front view showing another embodiment of the tripod type constant-velocity universal joint according to this invention;

[0040]FIG. 10 is a sectional view along line II-II of FIG. 9;

[0041]FIG. 11 is a perspective view showing a stopper ring of the embodiment of FIG. 9;

[0042]FIG. 12 is a sectional view showing how the tripod member is prevented from coming out;

[0043]FIG. 13 is a partially cutaway front view showing another embodiment; and

[0044]FIG. 14 is a perspective view showing a stopper ring of the embodiment of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0045] Hereinbelow, the embodiments of this invention will be described with reference to the drawings.

[0046] As shown in FIGS. 1 and 2, axially extending three track grooves 2 are formed in the inner periphery of an outer ring 1 at intervals of 120 degrees. Also, axially extending raceway grooves 3 are formed in side faces of each track groove 2, which oppose in the circumferential direction of the outer ring 1.

[0047] A tripod member 4 is mounted in the outer ring 1 and formed with three trunnions 5 at positions corresponding to the track grooves 2. A guide block 6 is supported on each trunnion 5. To support the guide blocks 6, a spherical surface 5 a is formed on each trunnion 5 and the trunnions 5 are inserted in cylindrical holes 7 formed in the guide blocks 6. The guide block 6 is pivotable in any direction relative to the trunnion 5.

[0048] In both side faces of each guide block 6, a pair of raceway grooves 8 opposing the raceway grooves 3 formed in both side faces of each track groove 2 of the outer ring 1 are formed. Between the opposed raceway grooves 3 and 8, rolling elements 9 comprising a plurality of balls are mounted.

[0049] The rolling elements 9, which are arranged in the axial direction of the outer ring 1 on both sides of each guide block 6, are retained by a retainer 10. Each retainer 10 is provided with retaining plate portions 10 b for retaining the rolling elements 9 on both sides of a plate portion 10 a arranged between the inner surface 11 of each track groove 2 and the outer face 12 of each guide block 6.

[0050] As described above, by mounting a plurality of rolling elements 9 between the raceway grooves 3 formed in side faces of each track groove 2 and the raceway grooves 8 formed in side faces of each guide block 6, it is possible to keep constant the position of the guide blocks 6. Thus, when the outer ring 1 and the tripod member 4 form a working angle, slip develops at the contact portion of the spherical outer surface 5 a of the trunnion 5 in the cylindrical hole 7 of the guide block 6, so that the trunnion 5 inclines relative to the axis of the cylindrical hole 7 of the respective guide blocks 6.

[0051] Thus, when torque is transmitted with the outer ring 1 and the tripod member 4 forming a working angle, the guide blocks 6 move in the axial direction of the outer ring along the track grooves 2 while keeping a constant position.

[0052] While the guide blocks 6 are moving, the rolling elements 9 move while rolling by contact with the raceway grooves 3 and 8, so that the moving resistance of the guide blocks 6 is extremely small. Thus, the guide blocks 6 will slide smoothly, so that during sliding, vibration is scarcely produced.

[0053] The moving distance of the rolling elements 9 during sliding of the guide blocks 6 is half of the moving distance of the guide blocks 6 if slipping at contact portions with the raceway grooves 3 and 8 is ignored. If there is a difference in the moving distance between the rolling elements 9 and the retainers 10, slip of the rolling elements 9 can occur, so that vibration is produced.

[0054] If the retainers 10 for retaining the rolling elements 9 are simply mounted between the side faces of the track grooves 2 and the side faces of the guide blocks 6, there is a fear that the retainers 10 may shift in the axial direction and fall off due to slipping at the contact portions of the rolling elements 9 in the raceway grooves 3 and 8, or due to vibration of an automobile in which is mounted a constant-velocity universal joint.

[0055] In order that all of the rolling elements 9 make pure rolling motion and will not fall from between the raceway grooves 3 and 8, the moving distance of the retainers 10 is restricted to half of the moving distance of the guide blocks 6 by means of the moving distance restricting mechanisms 20.

[0056] As shown in FIGS. 2 and 3, the moving distance restricting mechanism 20 is provided with a flat plate- shaped lever 21 on the outer surface of the plate portion 10 a of the retainer 10. The lever 21 is pivotable supported by caulking the end of a headed pin 22 such as a rivet that extends through both the central portion of the lever 21 and the plate portion 10 a, to couple the lever 21 to the retainer 10. A protrusion 23 comprising a pin secured to the outer ring 1 and a protrusion 24 secured to the guide block 6 are inserted in guide grooves 25 formed in the lever 21 so that the distances l₁ and l₂ from the respective protrusions 23, 24 to the pivot center of the lever are equal to each other. A cutout 26 into which the protrusion 24 secured to the guide block 6 is inserted is formed in the plate portion 10 a of the retainer 10 so that the guide block 6 and the retainer 10 can move relative to each other.

[0057] With the moving distance restricting mechanisms 20 having such a structure, since the ratio of the distance from the protrusion 23 on the outer ring 1 to the pivot center of the lever 21 to the distance from the protrusion 23 on the outer ring 1 to the protrusion 24 on the guide block 6 is 1:2, while the guide block 6 moves from the state shown in FIG. 4A to the state shown in FIG. 4C, the retainer 10 moves by half of the moving distance of the guide block 6. Thus, it is possible to make the moving distance of the retainer 10 equal to the moving distance of the rolling elements 9, which move by contact with the raceway grooves 3 and 8.

[0058] Thus, the plurality of rolling elements 9 are always in a rolling state over the entire moving range of the guide block 6, so that it is possible to achieve good NVH properties.

[0059] Also, since it is only necessary to ensure a distance sufficient to receive the lever 21 and the plate portion 10 a of the retainer 10 between the inner surface 11 of the track groove 2 and the outer surface 12 of the guide block 6, it is possible to prevent increase in the size of the outer ring 1, and thus to provide a compact constant-velocity universal joint.

[0060] Further, by forming the lever 21 into a flat plate shape, it can be easily formed by pressing.

[0061] Also, since the retainer 10 and the lever 21 are coupled together by caulking the pin 22, during assembling of the tripod type constant-velocity universal joint becomes easier.

[0062] In FIGS. 2 and 3, the flat plate-shaped lever 21 is provided on the outer side of the plate portion 10 a of the retainer 10. But as shown in FIG. 5, it may be provided on the inner side of the plate portion 10 a. In this case, a cutout 26 in which is inserted the pin 23 on the outer ring 1 is formed in the plate portion 10 a so that the guide block 6 and the retainer 10 can move relative to each other.

[0063]FIGS. 6 and 7 show another embodiment of the moving distance restricting mechanism 20 in which in the inner surface 11 of the track groove 2 are formed a pair of inclined grooves 30 a, 30 b extending axially and slant in opposite directions to each other. The radially outer surface of the guide block 6 is formed with inclined grooves 31 a, 31 b slant in opposite directions to the inclined grooves 30 a, 30 b so as to be opposed to the inclined grooves 30 a, 30 b. At the crossing points between the inclined grooves 30 a, 30 b on the outer ring 1 and the inclined grooves 31 a, 31 b on the guide block 6, balls 32 are accommodated and supported in a pair of guide grooves 33 formed in the plate portion 10 a of the retainer 10. The guide grooves 33 extend in a direction perpendicular to the direction in which the retainer 10 moves. The balls 32 can move along the guide grooves 33.

[0064] As described above, by provision of the inclined grooves 30 a, 30 b, 31 a and 31 b and by supporting the balls 32 at the intersections of the inclined grooves 30 a, 30 b, 31 a and 31 b with the guide grooves 33 formed in the plate portion 10 a so as to be movable in a direction perpendicular to the moving direction of the retainer 10, when the guide block 6 moves along the track groove 2, it is possible to move the retainer 10 by half of the moving distance of the guide block 6. Thus, it is possible to make the moving distance of the retainer 10 equal to the moving distance of the rolling elements 9, which move while rolling by contact with the raceway grooves 3 and 8.

[0065] Thus, the rolling elements 9, which bear the loads, are always in a rolling state, so that it is possible to achieve good NVH properties over the entire moving range of the guide block 6.

[0066] In order to allow all of the rolling elements 9 of the tripod type constant-velocity universal joints shown in FIGS. 2 and 6 to make purely rolling movement, the following conditional formulas have to be met. The position of each trunnion 5, which determines the positional relation between the guide block 6 and the outer ring 1, is set to substantially at the center of the sliding range in a reference position (in which the lever 21 is not inclined but perpendicular to the moving direction of the guide block 6).

K=(n−1)·A+L/2  formula (1)

B>A when n=2, B>2A when n>3  formula (2)

[0067] Symbols shown in FIG. 8 are as follows:

[0068] a: Diameter of the rolling elements 9

[0069] A: Pitch between the rolling elements 9 in each retainer 10

[0070] B: Length of the guide blocks 6

[0071] L: Required moving distance of the guide blocks 6

[0072] K: Length of the track groove of the outer ring

[0073] n: Number of rolling elements mounted in one raceway groove

[0074] nJ: rolling element number (J=1−n)

[0075] The following prerequisites are needed:

[0076] {circle over (1)} The load center of the tripod member in each guide block is at the longitudinal center.

[0077] {circle over (2)} The center of each guide block 6 is not outside of the rolling elements at both ends.

[0078] {circle over (3)} There are always two or more loaded rolling elements (n≧2).

[0079] {circle over (4)} The rolling element pitches are equal to each other and longer than the diameter of the rolling element (A>a).

[0080] When turning torque is transmitted with the tripod type constant-velocity universal joint forming a maximum working angle, each guide block 6 moves right and left by equal distances from the reference position of FIG. 8A to the position shown in FIGS. 8B and 8C. Assuming that the necessary moving distance of the guide block 6 is L,

[0081] {circle over (1)} The moving distance of the guide block to one side is L/2, and

[0082] {circle over (2)} The moving distance of the retainer 10 to one side is L/4.

[0083] {circle over (3)} Expressing the position of each rolling element 9 by a numerical formula when the guide block 6 is at the reference position of FIG. 8A

−(n−1)·A/2+(J−1)·A  formula {circle over (1)}

[0084] {circle over (4)} In order to allow all of the rolling elements 9 to make rolling motion over the entire moving range of the guide block 6, when the retainer 10 has moved −L/4 (the state shown in FIG. 8B), the guide block 6 must not fall off the rolling elements 9. For this purpose, it is necessary to satisfy the following three conditions i)-iii).

[0085] i) The right-hand end of the guide block 6 has to be on the right-hand side of the n2 rolling element.

[0086] From the formula {circle over (1)}, the position of the n2 rolling elements when the retainer 10 has moved −L/4 can be expressed as follows from the formula {circle over (1)},

−(n−1)·A/2+(J−1)·A−L/4  formula {circle over (2)}

[0087] On the other hand, expressing the position of the right-hand end of the guide block by a numerical formula, $\begin{matrix} {{{- \frac{L}{2}} + \frac{B}{2}} = \frac{B - L}{2}} & {{formula}\quad {◯3}} \end{matrix}$

[0088] Thus, in order to satisfy the conditions i), from the formulas {circle over (2)}, {circle over (3)}, the following has to be satisfied:

−(n−1)·A/2+(2−1)·A−L/4<(B−L)/2

[0089] Simplifying this formula;

(3−n)·A<B−L/2  formula {circle over (4)}

[0090] ii) The center of the guide block 6 has to be on the right-hand side of the n1 rolling element.

[0091] The position of the n1 rolling element when the retainer 10 has moved −L/4 can be expressed from the formula {circle over (1)} as follows:

(n−1)·A/2+(J−1)·A−L/4  formula {circle over (5)}

[0092] On the other hand, expressing the central position of the guide block 6 by a numerical formula,

−L/2  formula {circle over (6)}

[0093] Thus, in order to satisfy the conditions ii), from formulas {circle over (5)}, {circle over (6)}, the following must be satisfied.

−(n−1)·A/2+(J−1)·A−L/4<−L/2

[0094] Simplifying this formula; $\begin{matrix} {{{{\left( {1 - n} \right) \cdot {A/2}} - {L/4}} < {{- L}/2}} = {{\left( {1 - n} \right) \cdot A} < {{- L}/2}}} & {{formula}\quad {◯7}} \end{matrix}$

[0095] iii) If n=2, B>A has to be met, and if n≧3, B>2A has to be met.

[0096] {circle over (5)} With the conditions i), ii), iii) satisfied, the length K of the raceway grooves 3 of the outer ring 1 will be twice the n1 rolling element when the retainer 10 has moved by −L/4.

[0097] From formula {circle over (1)}, the position of the n1 rolling element when the retainer 10 has moved −L/4 can be expressed as follows: −(n − 1) ⋅ A/2 + (1 − 1) ⋅ A − L/4 = −(n − 1) ⋅ A/2 − L/4

[0098] Thus, the length K of the raceway grooves 3 will be: $\begin{matrix} {K = \quad {2 \cdot {{{{- \left( {n - 1} \right)} \cdot {A/2}} - {L/4}}}}} \\ {= \quad {{\left( {n - 1} \right) \cdot A} + {L/2}}} \end{matrix}$

[0099] Thus, it is possible to obtain the length K of the raceway grooves 3 of the outer ring.

[0100] For reference, if a tripod type constant-velocity universal joint in which L=40 mm, n=3 and a=10 mm is to be designed,

[0101] A will be A>10 mm from formula {circle over (7)}, and

[0102] Assuming that A=15 mm,

[0103] B will be B>30 mm from B>2A.

[0104] Thus, K=50 mm

[0105] But in determining the cup length of the outer ring, the length K of the outer ring raceway groove and the interference lengths of the outer ring inlet side and deeper side have to be taken into consideration. Thus the cup length of the outer ring has to be K+B/2 or over.

[0106] From the necessary moving distance of the guide block 6, the number n of the rolling elements, the length B of the guide block and the length K of the outer ring raceway grooves are determined. Since the guide block length and the outer ring raceway groove length vary with the number of rolling elements, optimum conditions are determined.

[0107] Normally, the guide block 6 has a necessary moving distance of 40 mm or over. Thus, assuming that L=40 mm and the symbol >1.1 times, the pitch A of the rolling elements, length B of the guide block, and length K of the outer ring raceway grooves for n=2, 3 and 4 will be as shown in Table 1. TABLE 1 n A (mm) B (mm) K (mm) K +B/2 (mm) 2 22 44 42 64 3 11 24.2 42 54.1 4 11 24.2 42 54.1

[0108] Thus, if n=2, both the guide block and outer ring cup length will be long. If n=4, the number of rolling elements is large. The number n of the rolling elements is preferably 3.

[0109] FIGS. 9 to 12 show the second embodiment of the tripod constant-velocity universal joint. It differs from the embodiments of FIGS. 1, 5 and 6 in that a stopper ring 20 formed by pressing a metallic plate is provided at the open end of the outer ring 1. As shown in FIGS. 9-11, stopper ring 40 has an annular plate portion 41 abutting the end of the outer ring 1. On the outer periphery of the annular plate portion 41, a cylindrical portion 42 is provided and pressed on the open end of the outer ring 1. The rear end of the cylindrical portion 42 is caulked inwardly. An annular bent portion 42 a formed by caulking engages in a groove 43 formed in the outer periphery of the outer ring 1. The engagement prevents the stopper ring 40 from moving in the axial direction.

[0110] Cutouts 44 are formed at positions opposing the track grooves 2 of the outer ring 1 (FIG. 11). Protrusions 45 provided on both sides of each cutout 44 are inserted in the raceway grooves 3 formed in the side surfaces of the track groove 2.

[0111] By mounting the stopper ring 40 having the above-described structure on the open end of the outer ring 1, when the tripod member 4 moves toward the open end of the outer ring 1 as shown in FIG. 12, the rollers 9 will abut the protrusions 45 provided on the stopper ring 40. The abutment prevents the retainer 10 from coming off.

[0112] The lever 21 provided on the plate portion 10 a of each retainer 10 is prevented from turning by the engagement of a pin 23 on the outer ring 1 in a guide groove 25 formed in the lever 21 (FIG. 10). Since a pin 24 provided on each guide block 6 is engaged in the other guide groove 25 formed in the lever 21, the guide blocks 6 and the tripod member 4, which supports the guide blocks 6, are prevented from coming out of the open end of the outer ring 1.

[0113]FIGS. 13 and 14 show another embodiment of the stopper ring 40 for preventing the tripod member 4 from coming out. This embodiment differs from the stopper ring 40 shown in FIG. 12 in that the stopper ring 40 is provided with three pin-forming pieces 46 in the respective cutouts 44 formed in the stopper ring 40 so as to be inserted in the respective track grooves 2 of the outer ring 1 and that a pin 47 is formed on the pin-forming piece 46 by pressing so as to be inserted into one guide groove 25 of the lever 21. Thus, to the same portions as those of the stopper ring 40 shown in FIG. 12, the same numerals are used, and their description is omitted.

[0114] As described above, by providing the pin 47 on each pin-forming piece 46, the pins 23 shown in FIG. 9 can be eliminated, so that the number of parts decreases. This makes it possible to reduce the cost. Also, since it is not necessary to fix the pins 23 to the outer ring 1, the tripod type constant-velocity universal joint is easier to assemble.

[0115] According to the present invention, a tripod type constant-velocity universal joint is designed so that all the rolling elements will roll over the entire moving range of the guide block in the axial direction of the outer ring. Thus a tripod type constant velocity universal joint is provided which has good NVH properties.

[0116] Also, according to the present invention, the length K of the track groove of the outer ring is determined to satisfy the formula K=(n−1)·A+L/2 wherein n is the number of the rolling elements mounted in one raceway groove, A is the pitch between the rolling elements and L is the required moving distance of the guide block and the length B of the guide block is longer than that of the pitch A between the rolling elements (B>A) if the number of the rolling elements is two and is longer than double the pitch A (B>2A), if the number of the rolling elements is three or more. This makes it possible to extremely easily provide a tripod type constant-velocity universal joint which has good NVH properties.

[0117] Also, by setting the number of the rolling elements mounted in one raceway groove to three, it is possible to provide a compact, light-weight tripod type constant-velocity universal joint which has a small axial length.

[0118] According to this invention, since the stopper ring is provided at the open end of the outer ring, it is possible to reliably prevent the tripod member from coming out of the open end of the outer ring.

[0119] Also, since the stopper ring is of a simple structure in which a plurality of cutouts are formed in the annular plate portion having a cylindrical portion on the outer periphery thereof, it can be formed easily by pressing a metallic plate. 

What is claimed is:
 1. A tripod type constant-velocity universal joint comprising an outer ring formed with three axially extending track grooves in inner periphery thereof, a tripod member mounted in said outer ring and having three trunnions formed thereon so as to oppose said track grooves, raceway grooves formed in side faces of said each track groove opposing each other in the circumferential direction of said outer ring, said raceway grooves extending in the axial direction of said outer ring, a guide block supported on said each trunnion so as to be pivotable relative to said trunnion and received in said each track groove, said guide block being formed with a raceway groove in side faces thereof, a plurality of rolling elements mounted between said raceway groove formed in side faces of said each guide block and said each raceway groove of said outer ring, retainers for retaining said rolling elements, and a moving distance restricting means for restricting the moving distance of said each retainer to half of the moving distance of said guide block, characterized in that said rolling members are adapted to roll over the entire moving range in the axial direction of said outer ring.
 2. A tripod type constant-velocity universal joint as claimed in claim 1 wherein the length of said raceway groove of said outer ring and the length of said guide block meet the following formula: K=(n−1)·A+L/2 B>A when n=2, B>2A when n≧3 wherein a: Diameter of the rolling elements A: Pitch between the rolling elements B: Length of the guide block L: Required moving distance of the guide block K: Length of the track groove of the outer ring n: Number of rolling elements mounted in one raceway groove
 3. A tripod type constant-velocity universal joint as claimed in claim 1 or 2 wherein the number of said rolling elements mounted in one raceway groove is three.
 4. A tripod type constant-velocity universal joint as claimed in claim 1 wherein said each retainer has a plate portion disposed between the inner surface of said each track groove and the outer surface of said each guide block, and said moving distance restricting means comprises a pivotable lever having its longitudinally central portion supported by said plate portion of said retainer, said pivotable lever being formed with a pair of guide grooves extending axially, and a pair of pins inserted in said guide grooves, one of said pair of pins being secured to said outer ring and the other being secured to said guide block.
 5. A tripod type constant-velocity universal joint as claimed in claim 1 or 4 wherein a stopper ring is mounted to the open end of said outer ring for preventing said rolling elements from coming out of said outer ring.
 6. A tripod type constant-velocity universal joint as claimed in claim 5 wherein said stopper ring has an annular plate portion abutting the open end of said outer ring, a cylindrical portion provided on the outer periphery of said annular plate portion and fitted on the outer periphery of the open end of said outer ring, said annular plate portion being formed with cutouts at positions opposing the open ends of said track grooves, and protrusions provided on both sides of said each cutout and inserted in said raceway grooves of said outer ring to prevent said rolling elements from coming out of the open ends of said track grooves.
 7. A tripod type constant-velocity universal joint as claimed in claim 6 wherein a pin-forming piece is formed on the inner periphery of said each cutout of said annular plate portion of topper ring so as to be inserted in said each track groove, and said pin secured to said outer ring is formed by pressing on said each pin-forming piece.
 8. A tripod type constant-velocity universal joint as claimed in any of claims 5-7 wherein said stopper ring is formed by pressing a metallic plate. 